The present invention relates to refrigeration apparatus and more particularly to a multi-compartment refrigerator appliance, a refrigeration apparatus with evaporator heater for defrosting the evaporator and/or an automatic ice maker.
Multi-compartment refrigerator appliances are known, and in particular, there are dual compartment domestic refrigerator/freezer appliances such as disclosed in U.S. Pat. Nos. 4,416,119 and 5,255,530.
In the ""119 patent, separate evaporators are used for controlling the temperature of the separate compartments.
In the ""530 patent, a single evaporator, condenser and compressor are utilized for cooling two different compartments to different temperature levels by controlling air flow between the compartments. A variable speed motor drives the compressor, a variable speed condenser fan moves air over the condenser and a variable speed evaporator fan circulates air over the evaporator and to the two different compartments one of which is a freezer compartment and one of which is a fresh food compartment. The temperature of the fresh food compartment is controlled by varying the speed of the evaporator fan and the temperature of the freezer compartment is controlled by varying the speed of the evaporator fan and compressor motor.
U.S. Pat. No. 5,555,736 discloses a two compartment refrigeration appliance in which the temperature in the freezer compartment is controlled by varying a speed of the compressor motor and evaporator fan in response to a generated error signed comprising the difference between a sensed temperature and a manually set desired temperature. The temperature of the fresh food compartment is controlled by varying a speed of the evaporator fan and by controlling the position of an openable damper between the fresh food compartment and the freezer compartment.
U.S. Pat. No. 6,185,948 discloses a two compartment refrigeration appliance in which the temperature in each compartment is controlled through the use of a separate evaporator and evaporator for dedicated to each compartment.
Controls for selectively defrosting an evaporator are known, for example, as disclosed in U.S. Pat. Nos. 4,689,965 and 5,469,715.
In the ""965 patent the evaporator heater is run continuously during a defrost cycle and the time required for defrosting is used to adjust a length of time for the next cooling cycle before a next defrost cycle is required.
In the ""715 patent a defrost cycle controller is disclosed which utilizes a continuously operating evaporator heater during a defrosting cycle.
Ice maker controls and methods for operating ice makers are known, such as those disclosed in U.S. Pat. Nos. 3,611,741 and 4,424,683.
In the ""741 patent an evaporator fan is operated continuously during ice making operation and the duration of the ice making operation is controlled by an ice maker thermostat switch 32.
In the ""683 patent, a calculating means is used to calculate a time for effecting a freezing of water in the ice making device dependent upon sensed temperatures in the freezer compartment and a determination of whether an evaporator fan is operating. Depending on whether the evaporator fan is on or off and whether a sensed temperature is above or below a predetermined temperature, a different calculation is made for determining whether sufficient time has passed for ice formation.
The present invention, in various embodiments, can be practiced in a refrigeration appliance, such as one with a freezer compartment and a fresh food compartment, in some embodiments in a refrigeration appliance having an automatic maker present in a freezer compartment, and in some embodiments in a refrigeration appliance having a control for defrosting an evaporator.
In an embodiment of the invention an evaporator fan is used to supply air to two or more compartments of a refrigeration appliance. The temperature in each compartment may be separately controlled. The speed of the evaporator fan is controlled by the sensed need for cooling of each compartment.
The state of each compartment is determined and compared. The compartment with the greater need for cooling will control the fan speed. A sensor, such as a thermistor, is placed in each compartment to determine the actual temperature of the compartment. This temperature is compared to a set point of the compartment set by the user. The difference between the set point and the thermistor temperature is called the error condition for the compartment. The sensor is monitored for a period of time to determine a rate of change for the compartment temperature. The error condition and the rate of change are combined and are referred to as the state of the compartment.
In an embodiment of the invention, the refrigeration system includes a variable capacity compressor, a fixed speed alternating current condenser fan, a direct current variable speed evaporator fan and a variable position damper.
In an embodiment of the invention a refrigeration appliance is provided which has a first compartment to be cooled, at least one evaporator in heat transfer association with the first compartment, defrost heater associated with the evaporator, a temperature sensor associated with the evaporator and a control circuit. The control circuit is arranged to selectively energize the defrost heater during a defrost cycle, to generate a timing signal while the defrost heater is de-energized during the defrost cycle, and the control circuit is arranged to receive an input from the temperature sensor and an accumulation of time from the timing signal.
A defrost cycle can be performed by this refrigeration appliance in which the evaporator is operated to cool the first compartment, the defrost cycle is initiated to defrost the evaporator, the evaporator heater is energized to heat the evaporator, a temperature of the evaporator is monitored with the temperature sensor, the evaporator heater is de-energized once a cut-off temperature is sensed, a time is accumulated that the evaporator is de-energized and the evaporator is re-energized to heat the evaporator upon reaching a specified accumulated time. The temperature of the evaporator is monitored with the temperature sensor and if the temperature is below the cut-off temperature the above steps are repeated once the cut-off temperature is reached. If the temperature is at or above the cut-off temperature, the evaporator heater is continued to be energized until the evaporator temperature reaches a pre-determined optimum temperature and thereafter the defrost cycle is terminated.
The control circuit in this embodiment may operate to include a step of waiting for a drip time to pass before terminating the defrost cycle and the drip time may have a length dependent upon an accumulated total time that the evaporator heater has been energized. The control circuit might further include a delaying operation of an evaporator fan after termination of the defrost cycle until a sensed temperature of the evaporator has fallen below a predetermined cooling temperature.
In an embodiment of the invention, the control circuit repeatedly energizes and de-energizes the defrost heater during the defrost cycle and terminates the defrost cycle after the evaporator has reached a predetermined optimum temperature.
In an embodiment of the invention an ice maker is provided in a freezer compartment, the ice maker including a mold for receiving water in which to form ice bodies and an ice storage bin. The appliance also includes a fresh food compartment with the freezer compartment and the fresh food compartment cooled by means of an evaporator in thermal communication with both compartments and a fan to direct a stream of air over the evaporator and through both compartments. A method is provided in which a fill level of the ice storage bin is monitored, and when the ice level is below a desired full level, a charge of water is dispensed into the mold. An alternate cooling routine is initiated by energizing a motor of the evaporator fan for a sufficient period of time to freeze the water in the mold. During this time, the temperature in the fresh food compartment is monitored and controlled by selectively allowing and preventing the air stream from passing through the fresh food compartment. If desired, the temperature in the freezer compartment may be monitored and controlled by energizing and de-energizing the compressor, or the compressor may remain energized during the entire alternate cooling routine. The ice bodies are dispersed from the mold to the storage bin upon completion of the freezing time. If the storage bin is the full, the alternate cooling routine is terminated. Otherwise a new charge of water is introduced to the mold and the process is repeated.